From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754959AbbI3HbZ (ORCPT ); Wed, 30 Sep 2015 03:31:25 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:57070 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754387AbbI3HbR (ORCPT ); Wed, 30 Sep 2015 03:31:17 -0400 Message-Id: <20150930072304.285433585@infradead.org> User-Agent: quilt/0.61-1 Date: Wed, 30 Sep 2015 09:10:42 +0200 From: Peter Zijlstra To: mingo@kernel.org Cc: linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, fweisbec@gmail.com, oleg@redhat.com, umgwanakikbuti@gmail.com, tglx@linutronix.de, rostedt@goodmis.org, Peter Zijlstra Subject: [PATCH v2 07/12] sched: Robustify preemption leak checks References: <20150930071035.514587432@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peterz-kill-preempt_active-3.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When we warn about a preempt_count leak; reset the preempt_count to the known good value such that the problem does not ripple forward. This is most important on x86 which has a per cpu preempt_count that is not saved/restored (after this series). So if you schedule with an invalid (!2*PREEMPT_DISABLE_OFFSET) preempt_count the next task is messed up too. Enforcing this invariant limits the borkage to just the one task. Reviewed-by: Frederic Weisbecker Reviewed-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) --- kernel/exit.c | 4 +++- kernel/sched/core.c | 4 +++- 2 files changed, 6 insertions(+), 2 deletions(-) --- a/kernel/exit.c +++ b/kernel/exit.c @@ -706,10 +706,12 @@ void do_exit(long code) smp_mb(); raw_spin_unlock_wait(&tsk->pi_lock); - if (unlikely(in_atomic())) + if (unlikely(in_atomic())) { pr_info("note: %s[%d] exited with preempt_count %d\n", current->comm, task_pid_nr(current), preempt_count()); + preempt_count_set(PREEMPT_ENABLED); + } /* sync mm's RSS info before statistics gathering */ if (tsk->mm) --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2968,8 +2968,10 @@ static inline void schedule_debug(struct BUG_ON(unlikely(task_stack_end_corrupted(prev))); #endif - if (unlikely(in_atomic_preempt_off())) + if (unlikely(in_atomic_preempt_off())) { __schedule_bug(prev); + preempt_count_set(PREEMPT_DISABLED); + } rcu_sleep_check(); profile_hit(SCHED_PROFILING, __builtin_return_address(0));